Beneficiation of calcite-apatite-quartz ores



United States Patent 3,534,854 BENEFICIATION OF CALtIiTlE-APATHTE- QUARTfl OllilEfl Glen K. Korpi, Highland Park, and Qraig S. Wiedernann, Glenview, Ill., assignors to International Minerals 81 Chemical Corporation, a corporation of New York No Drawing. Filed Nov. 20, 1967, Ser. No. 684,548 Int. Cl. B03111 1/02 US. Cl. 209166 6 Claims ABSTRACT OF THE DISCLOSURE Disclosed is a process for beneficiating a finely divided mixture of particles of calcite and apatite or the like. The mixture of particles is subjected to froth flotation in an aqueous medium in the presence of an anionic collector and at an elevated pH to produce a float concentrate relatively richer in calcite than the original mixture and an unfloated sink residuum relatively richer in apatite than the original mixture. The calcite-rich float concentrate and the apatite-rich sink residuum may be collected separately. If the original mixture includes a significant amount of siliceous material such as quartz, the bulk of the same will be present in the apatite-rich sink residuum which may be subjected to further anionic froth flotation at a lower pH to produce a second float concentrate relatively richer in apatite than the sink residuum and a tailing product relatively richer in quartz than the sink residuum. The apatite-rich second float concentrate and the quartzrich tailing product may also be collected separately.

BACKGROUND OF THE INVENTION This invention generally relates to froth flotation beneficiation of minerals. In a particular aspect, it relates to froth flotation beneficiation of calcitic phosphate ore. Still more particularly, it relates to the recovery of a phosphate concentrate from ores containing calcite and apatite as the principal mineral constituents. The novel process of this invention is applicable for the beneficiation of calcite-apatite ores in which these principal mineral are substantially liberated from each other.

Calcite is essentially calcium carbonate (CaCO and typically includes approximately 56.0% CaO and 44.0% CO Apatite is essentially a calcium phosphate varying widely in chemical composition, but usually containing Cl, F and 00 in its crystal lattice. Apatite is a common mineral and appears in small amounts in practically all igneous rocks. Concentrations rich enough to justify mining are found in many localities. The mineral apatite is preferably in concentrated form for its major uses. The phosphate industry requires a phosphatic material of relatively high BP-L content (bone phosphate of lime, Ca (PO for the production of fertilizers, such as superphosphate and triple superphosphate, and phosphoric acid, and imposes price penalties where impurities are present in excess of certain maximum fixed percentages.

In order to be attractive on a commercial scale, a process for beneficiating a phosphate ore should produce a phosphate concentrate which is substantially free of gangue 3,534,854 Patented Oct. 20, 1970 'ice minerals. Many methods have been devised to beneficiate phosphate ores. Froth flotation beneflciation of phosphate minerals is commercially practiced on phosphate ores in which silicate minerals are the predominant gangue. Prior to the present invention, however, it has been extremely diflicult to beneficiate calcitic phosphate ores with any substantial commercial success. As for example, the patents to Snow, US. 'Pat. Nos. 3,022,890 and 3,259,242, disclose methods for beneflciating apatite-calcite ores which have inherent shortcomings limiting their application. For example, the electrostatic process of Pat. No. 3,022,890 requires highly specialized apparatus, while the process of Pat. No. 3,259,242 requires the use of both anionic and cationic collector agents. Thus, operational procedures and equipment are complex.

Accordingly, it is a major object of the present invention to provide an improved process for beneficiating a calcite-apatite ore.

A further object of the present invention is to provide a froth flotation process for beneficiating a calcite-apatite ore, wherein the complexity of the process itself, as well as the equipment required for carrying out the same, is reduced to a minimum.

The presence of quartz in calcite-apatite ores, has always interfered with the effective beneficiation of the ore. Hence, another very important object of the instant invention is to provide a process whereby calcite-apatite-quartz mixed ores are beneficial to produce a calcite-rich fraction and an apatite-rich fraction, each of which is relatively free of the other mineral as well as of quartz. Finally it is an object of the present invention to minimize, if not eliminate completely, the various commercial shortcomings of the prior processes directed to beneficiation of apatitecalcite ores.

SUMMARY OF THE INVENTION In accordance with the present invention, it has been discovered that eminently satisfactory beneficiation of apatite-calcite-quartz ores can be achieved by froth flotation in a series of critical and interdependent process steps.

In one aspect, the present invention is directed to a process for beneficiating a calcite-apatite ore which comprises subjecting a mixture containing discreet particles of apatite and calcite minerals to anionic flotation (froth flotation in an aqueous medium in the presence of an anionic flotation reagent such as fatty acid) at a pH of at least about 10 whereby the calcite is floated and the bulk of the apatite remains in the nonfloated sink residuum.

In another, more specific aspect, the present invention is directed to an improved process for beneiiciating a calcite-apatite-quartz ore which comprises subjecting a mixture containing finely divided calcite, apatite and quartz particles to anionic flotation in an aqueous medium at a pH of at least about 9 to produce a first float concentrate relatively richer in calcite than the original mixture of particles. Also produced is a first sink residuum which is relatively richer in apatite and quartz particles than the original mixture. The float concentrate is collected and recovered as a calcite-rich product. Thereafter, the first sink residuum is subjected to further anionic flotation in an aqueous medium at a pH within the range of about prises the bulk of the quartz present in the original mixture. The second float concentrate (from the low pH anionic flotation) is collected and recovered as an apatiterich product.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Ores which may be beneficiated by the method of the present invention are the natural calcite-apatite ores which may contain other minerals such as dolomite, quartz and the like; Specifically, the method of this invention has particular commercial utility in the beneficiation of natural calcite-apatite ores containing quartz. Examples of ores which may be beneficiated by the process of this invention include North Carolina ores, a typical assay of which is 8.24% P 9.96% C0 (1.93% bound), and 54.69% SiO (this typical North Carolina ore has a mineralogical composition of approximately 36.9% apatite, 11.4% calcite, and 51.8% quartz); Western ores, a typical assay of which is 24.60% P 0 3.29% C0 (1.79% bound), and 26.6% SiO and Sahara ores, a typical assay of which is 32.08% P 0 4.49% C0 (1.52% bound), and 7.84% SiO In addition to the naturally occurring calcite-apatite ores, the process of the present invention may also be used for beneficiating artificially created mixtures or concentrates obtained in various benefication processes.

Regardless of the source of the ore, it is necessary that the apatite and calcite each be substantially liberated from other components of the mixture and from each other and be of a mesh size amenable to froth flotation operation. Accordingly, the materials to be treated are, where necessary, reduced to a particle size of less than about mesh and preferably to a particle size of less than mesh. The lower limit of useful particle size is about 325 mesh and desirably the particles will be coarser than about 200 mesh since phosphatic material finer than about 200 mesh is not effectively separated by a froth flotation.

The liberated mixture containing discreet particles of apatite and calcite minerals is preferably washed to remove slimes fined than about 44 microns. Such desliming operations are well known in the phosphate mineral benefication industry. The deslimed mixture is then subjected to anionic flotation.

Th anionic flotation may employ any suitable anionic (or negative ion) flotation reagent (or collector). Many 1 standard anionic flotation reagents are known to the art. The particular anionic reagent utilized in the anionic froth flotation does not constitute an essential feature of this invention which is operable with and contemplates the use of all such reagents. Representative conventional anionic reagents include fatty acids or fatty acid soaps, particularly mixed fatty acids or soaps thereof; fatty acids or soaps derived from natural sources such as tall oils; fatty acids or soaps of acids derived from animal and vegetable oils and fats; esters of inorganic acids with high molecular weight alcohols; and the like.

The particulate mixture may be conditioned with the flotation reagent in conventional manner and in conventional amount. The flotation reagent is generally used in amount of from about 0.1 to about 5.0 lbs. of flotation reagent per ton of solids treated. The reagentized mixture is then subjected to froth flotation employing any suitable equipment. Standard flotation equipment or flotation cells are well known in the art. As a first process step, the reagentized mixture is subjected to anionic flotation at a pH of at least about 9 and preferably within the range of from about 10 to about 12. A basic material, such as sodium or potassium hydroxide, is used to raise the pH to the desired level. This flotation is effective to produce a float concentrate which is relatively richer in calcite than the original particulate mixture. Furthermore, a sink residuum is produced which is relatively richer in both apatite and quartz (if the latter is also present) than the original particulate mixture.

The calcite-rich float concentrate produced in this high pH anionic flotation step is collected and removed from the surface of the flotation medium in a conventional manner. The concentrate comprises a calcite-rich product which may be further concentrated by additional beneficiation processes. If a siliceous mineral such as quartz is present in the original mixture, the major portion of the same will be present in the apatite-rich sink residuum. If it is desired to separate the quartz from the apatite, the pH of the flotation medium is then reduced to within the range of from about 6.0 to about 7.5 and preferably from about 6.5 to about 7.0. Also, at this time, a sufficient amount of anionic collector is added to the flotation medium to compensate for the amount of the same carried away with the calcite-rich float concentrate.

Anionic flotation is resumed at this lower pH level to produce a second float concentrate relatively richer in apatite than the residual sink material produced during the high pH anionic flotation. This apatite-rich product may also be subjected to further beneficiation if desired. The tailing product produce during this low pH anionic flotation comprises the bulk of the quartz originally present in the particulate mixture.

The pH of the flotation medium may be reduced by introducing thereinto a quantity of an acid and preferably a mineral acid such as hydrochloric acid. Thereafter, the low pH anionic flotation is conducted in essentially the same manner as the high pH anionic flotation.

Thus, by following the concepts and principles of the instant invention, calcite may be separated by flotation from apatite at a relatively high pH, that is above about 9, without resorting to the use of modifying agents. It the ore also contains appreciable amounts of quartz, it may also be removed from the apatite by adjusting the pH of the flotation medium to a lower value of approximately within the range of about 6 to about 7.5, addin additional anionic collector and removing the apatite as a floated product.

In order to give a fuller understanding of the invention but with no intention to be limited thereto, the following specific examples are given:

EXAMPLE I Twenty grams of a finely divided North Carolina ore, having an assay as set forth above, were mixed for about two minutes with a flotation medium comprising 500 milliliters of a water solution including 4 10 equivalents of neutralized oleic acid (as potassium oleate) and a suflicient quantity of potassium hydroxide to produce a pH of approximately 10.6 therein. Agitation of the mixture was then discontinued, and the anionic flotation was initiated and continued for approximately one minute. This flotation produced a calcite-rich float concentrate which was removed from the surface of the aqueous flotation medium as a calcite-rich product. Thereafter, sufficient water was added to return the volume of the system to 500 milliliters and 5X l() equivalents of the collector and 8X10 equivalents of HCl were also added. The former was added to replenish the supply of anionic collector and the latter was added to reduce the pH of the system to approximately 6.8. Immediately upon addition of these reagents a second anionic flotation was commenced and was continued for approximately two minutes. An apatite-rich second float concentrate was produced and recovered from the surface of the aqueous flotation medium as an apatite-rich product. The non-floated sink material remaining at the bottom of the flotation medium following the second anionic flotation was removed as a quartz-rich product. The analytical and metal- 5 lurgical results of this test are reproduced in Table 1 below:

TAB LE 1 Apatite Calcite Quartz Product float float sink Totals (1) Wt. percent 22. 9 21. 4 55. 7 100.00 (2) Percent P20 27.85 3. 55 1. 95 6. 39 0.76 1. 09 8. 24 77. 55 9. 22 13. 23 100. 6. 87 38. 1 0. 43

1. 57 8. 15 O. 24 9. 15.76 81.83 2. 41 100.00 (8) Percent S102 4. 88 6. 87 93. (9) Units 810; 1.12 1. 47 52.1 54. 69 Percent Dist. S102 2.05 2. 69 95. 26 100. 00

In Table 1 above (and Tables 2 and 3 below) the figures in row (1) show the weight of ore in each product as a percent of the original amount of ore originally subjected to treatment. The figures in rows (2), (5) and (8) show the amount of each of the indicated chemicals in each product expressed as a weight percent of the ore in each product respectively. The figures in rows (3), (6) and (9) show the weight of the indicated chemical in each product if 100 weight units of ore had been originally treated. The figures in rows (4), (7) and (10) show the amount of each indicated chemical in each product, expressed as a weight percent of the total amount of the particular chemical present in the original ore sample. Examining the numbers listed in Table 1 in the column corresponding to Apatite Float, 22.9% by weight of the total ore was present in the apatite-rich float concentrate. This 22.9% of the ore was 27.85 wt. percent P 0 6.87 wt. percent CO and 4.88 wt. percent SiO Thus, if the original sample had been 100 gms., the apatite-rich float concentrate would include 6.39 gms. of P 0 1.57 gms. of CO and 1.12 gms. of SiO Therefore, this apatite-rich float concentrate, which contained only 22.9% of the original ore, contained 77.55% of the P 0 present in the original ore. Further, this apatite-rich product contained only 15.76% of the CO and 2.05% of the Si0 from the original ore.

EXAMPLE II A gram sample of a finely divided Sahara ore, having an assay as set forth above, was mixed with a flotation medium comprising 500 milliliters of a water solution including 4 l0 equivalents of neutralized oleic acid (as potassium oleate) and a suflicient quantity of potassium hydroxide to produce a pH of approximately 10.3 therein. The mixture was agitated for several minutes and anionic flotation was initiated and continued for approximately one minute. This flotation produced a calcite-rich float concentrate which was removed from the surface of the aqueous float medium as a calcite-rich product. The non-floated residuum sink material remaining at the bottom of the flotation medium was removed as an apatiterich product. A second flotation was not performed in this experiment. The analytical and metallurgical results of this test are reproduced in Table 2 below:

EXAMPLE III Twenty grams of a finely ground Western ore, having an assay as set forth above, were mixed with a flotation medium comprising 500 milliliters of a water solution including 4 l0" equivalents of, neutralized oleic acid (as potassium oleate) and a suflicient quantity of potassium hydroxide to produce a pH of approximately 11.6 therein. The mixture was agitated for several minutes and anionic flotation was initiated and continued for approximately one minute. This flotation produced a calciterich float concentrate which was removed from the surface of the aqueous float medium as a calcite-rich product. The non-floated residuum sink material remaining at the bottom of the flotation medium was removed as an apatite'rich product. Again, as in Example II, a second flotation was not performed. The analytical and metallurgical results of the test are reproduced in Table 3 below:

TABLE 3 Calcite Apatite Product float sink Totals (1) Wt. percent 18. 8 81. 2 100. 0 (2) percent P20 25. 9 24. 3 (3) Units P20,. 4. 87 19. 73 24. 60 (4) Dist. P20 19. 8 80. 2 100. 0 (5) Percent C00 6. 45 2. 56 (6) Units C02. 1. 21 2. 08 3. 29 (7) Dist. 002 36. 8 63. 2 100.0 (8) Percent S 17. 1 28. 8 (9) Units SiOz. 3. 2 23. 4 26. 6 (10) Dist. SiO; 12. 0 88.0 100.0

The above examples illustrate that excellent beneficiation of calcite-apatite ores and of calcite-apartite-quartz ores may be achieved in accordance with the present invention.,

The description of the invention utilized specific reference to certain details; however, it is to "be understood that such details are illustrative only and are not given with the intention of limiting the scope of the invention. Other modifications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description.

We claim: 1. A froth flotation process for separating a finelydivided mixture containing apatite, calcite and quartz, which comprises the steps of:

subjecting said mixture to a flotation operation utilizing an anionic reagent and an aqueous medium at a pH of at last about 9 to produce a first float product which is relatively richer in calcite than said mixture and a sink residuum which is relatively richer in apatite and quartz than said mixture; collecting said first float product; reducing the pH of said aqueous medium to within the range of from about 6 to about 7.5;

subjecting said sink residuum to a second flotation operation utilizing said anionic reagent and aqueous medium to produce a second float product which is relatively richer in apatite than said sink residuum and a tailing material which is relatively richer in quartz than said sink residium; and

collecting said second float product.

2. A process in accordance with claim 1 wherein said mixture is a liberated ore, said first flotation operation is conducted while the pH of said aqueous medium is within the range of from about 10 to about 12, and said second flotation operation is conducted while the pH of said aqueous medium is within the range of from about 6.5 to about 7.0.

3. A process in accordance with claim 2 wherein a mineral acid is introduced into said aqueous medium, after said first float product is collected, in an amount to reduce the pH thereof to within the range of from about 6.5 to about 7.0.

4. A process in accordance with claim 3 wherein a quantity of said anionic reagent is removed with said first float product, and a suflicient amount of said anionic reagent is introduced into said aqueous medium, after said first float product is collected, to compensate for the quantity of said anionic reagent removed with said first float product.

5. A process in accordance with claim 4 wherein said 2,116,727 anionic reagent is a fatty acid. 2,125,852 6. A process in accordance with claim 4 wherein said 2,701,057 anionic reagent is a fatty acid soap. 3,113,838

References Cited UNITED STATES PATENTS 2,105,807 1/1938 Crago 209167 Perri et a1.

5 TIM R. MILES, Primary Examiner R. HALPER, Assistant Examiner 

